pH and indicators

2 marks · Normal

Name two indicators that can distinguish between an acid and an alkali, and state the colour each shows in an alkali.

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Also accept: Litmus (blue), methyl orange (yellow), phenolphthalein (pink)

Common mistakes: Listing indicators without stating colour; Giving acid colours

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Marking points

B1 · 1 mark · Any correct indicator for alkali/acid distinction stated (e.g. litmus, methyl orange, phenolphthalein).

B1 · 1 mark · States correct colour in alkali for each indicator named.

Worked solution

Litmus turns blue in alkali; methyl orange turns yellow; phenolphthalein turns pink. Any two accepted.